[Dnsmasq-discuss] DHCPv6 - network booting 'address in use'

Geert Stappers stappers at stappers.nl
Wed Sep 15 19:22:42 UTC 2021


On Wed, Sep 15, 2021 at 08:23:47AM +0200, Harald Jensas wrote:
> On 9/14/21 21:12, Geert Stappers via Dnsmasq-discuss wrote:
> > On Tue, Sep 14, 2021 at 04:58:10PM +0200, Harald Jensas wrote:
> > > Hi,
> > > 
> > > We are seeing an issue whit network booting over DHCPv6 is failing.
> > > The UEFI firmware is starting two DHCPv6 transactions, with separate IAID's.
> > > Initially one transactions succeeds, while the other transaction fails
> > > because the same address (fd42::200) is advertised.
> > > 
> > > On error, the client tries to recover by restarting the transaction with a
> > > new SOLICIT, the second address (fd42::201) in the host's range
> > > [fd42::200/126] is advertised by dnsmasq.
> > > 
> > > Despite requesting the second address, the dnsmasq is refusing the lease:
> > > dnsmasq-dhcp: 14744450 nest size: 16 option: 13 status  1 address in use
> > > dnsmasq-dhcp: 14744450 sent size: 24 option: 13 status  2 no addresses available
> > 
> > Why the   /126?
> > 
> 
> When network booting with DHCPv6 different stages in the boot process may
> not use the same IAID. The /126 reseves a range of IPv6 address to the host,
> in the case where the previous stage in the chain did not release it's lease
> allocating a range ensures there are addresses available for the subseqent
> steps.

Ah, thanks.  The dnsmasq manual page even states the /126

(Wild???) idea to get beyond current obstacle: Try  /125


Other thing to consider:  Make with a network sniffer a libpcap file
with the capture on DHCPv6, put it on a webserver and share the wget URL.
It enables more people to see what is going over the wire.


Groeten
Geert Stappers
-- 
Silence is hard to parse



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